In an LTE system, the positioning method of TA+AoA is a common positioning method. The positioning precision achieved in this method depends on the accuracy of TA and AoA measurements.
The positioning method of cell_D is a positioning method based upon cell coverage in which the location of a target UE is estimated by using known serving cell geographical information. The serving cell information can be obtained through calling, paging, updating Tracking Area (TA) or other ways. The method of TA+AoA further takes into account factors including a Timing Advance (TA) and an Angle of Arrival (AoA) on the basis of the positioning method of cell_ID to thereby achieve the purpose of more precise positioning.
A base station obtains an AoA of a transmission signal of a UE over an intelligent antenna, where the UE resides on a ray starting with the eNB, and the angle of the ray rotating counterclockwise from the true north is the AoA.
The Timing Advance (TA) can be obtained in two ways, and the TA obtained in the two ways are referred to as TA Type 1 and TA Type 2 respectively, where the TA Type 1 is generally obtained through the calculation of adding the time difference between User Equipment (UE) reception and transmission reported from the UE to a signal reception time difference measured by the base station, and the TA Type 2 is generally obtained by the base station through the measurement in a dedicated random access procedure. The value of the TA multiplied by the velocity of light and then divided by 2 is the distance between the UE and the base station, and the UE resides on a circle with its center being the base station and its radius being the distance between the user equipment and the base station. Location information of the user equipment can be obtained further according to angle information of the AoA, as illustrated in FIG. 1.
The positioning method of TA+AoA is typically used for network-based positioning primarily for the reason that the AoA typically can only be obtained by the base station through measurements, and both the TA Type 1 and the TA Type 2 are also obtained by the base station through calculations or measurements, that is, all the measurement values related to the positioning method are determined by the base station. These measurement values can also be provided by the base station to a positioning server which performs the positioning. In the meantime, some user equipment which does not support the positioning service can also be positioned by this method.
When positioning, an E-SMLC obtains the measurement capability of the user equipment, the positioning server decides all the parameters required to be measured, the base station starts relevant measurements and reports relevant measurement results and location information, and the positioning server performs location calculations.
A positioning flow of the positioning method of TA+AoA will be described below in details:
In a first scenario, the positioning is performed by using measurement results of TA Type 1+AoA as illustrated in FIG. 2 particularly as follows:
Step S201: an MME receives a positioning request for a UE, where the positioning request can be a positioning request initiated by the UE in an NAS layer message to obtain its own location information, or a positioning request initiated by a locating service client (LCS client) to the MME to obtain location information of the UE;
Step S202: the MME initiates the positioning request to an E-SMLC;
Step S203: the E-SMLC inquires about the positioning capability of the UE;
Step S204: the E-SMLC receives positioning capability information returned from the UE;
Step S205: the E-SMLC sends a measurement request message to a base station;
Step S206: the E-SMLC receives a response message returned from the base station;
Step S207: the base station sends a measurement control command to the UE;
Step S208: the base station triggers a physical layer to measure a TA and an AoA of the user equipment;
Step S209: the base station receives a measurement report returned from the user equipment;
Step S210: the base station returns measurement results to the E-SMLC;
Step S211: the E-SMLC determines the location of the user equipment according to the measurement results;
Step S212: the E-SMLC returns a positioning result to the MME; and
Step S213: the MME returns the positioning result to the client requesting the positioning.
In a second scenario, the positioning is performed by using measurement results of TA Type 2+AoA as illustrated in FIG. 3 particularly as follows:
Step S301: an MME receives a positioning request for a UE, where the positioning request can be a positioning request initiated by the UE in an NAS layer message to obtain its own location information, or a positioning request initiated by a locating service client (LCS client) to the MME to obtain location information of the UE;
Step S302: the MME initiates the positioning request to an E-SMLC;
Step S303: the E-SMLC inquires about the positioning capability of the UE;
Step S304: the E-SMLC receives positioning capability information returned from the UE;
Step S305: the E-SMLC sends a measurement request message to a base station;
Step S306: the E-SMLC receives a response message returned from the base station;
Step S307: the base station triggers a dedicated random access procedure to measure a TA Type 2;
Step S308: the base station triggers a physical layer to measure an AoA of the user equipment;
Step S309: the base station returns measurement results to the E-SMLC;
Step S310: the E-SMLC determines the location of the user equipment according to the measurement results;
Step S311: the E-SMLC returns a positioning result to the MME; and
Step S312: the MME returns the positioning result to the client requesting the positioning.
In the LTE-Advanced (LTE-A) system, peak rates have been increased greatly over those in the LTE system, where downlink 1 Gbps and uplink 500 Mbps are required. Meanwhile the LTE-A system is required to be well compatible with the LTE system. In order to meet the requirements of increased peak rates, compatibility with the LTE system and full use of spectrum resources, the Carrier Aggregation (CA) technology has been introduced to the LTE-A system.
The carrier aggregation technology refers to a mechanism in which multiple cells can be aggregated concurrently for the UE to provide the UE concurrently with data transmission service. In the carrier aggregation system, carriers corresponding to respective cells can be consecutive or inconsecutive in the frequency domain. For compatibility with the LTE system, the maximum bandwidth of each component carrier is 20 MHz, and bandwidths between respective component carriers can be the same or different.
With carrier aggregation, cells in which the user equipment operates include a primary cell (PCell) and several secondary cells (SCells), where the primary cell is responsible for a majority of control and signaling operations, such as transmission of an uplink feedback for downlink data, reporting of CQI, uplink pilot frequency transmission, etc., and the secondary cells are generally used as resources and responsible for data transmission.
In carrier aggregation scenarios, since different carriers may exist in different propagation environments, for example, at different frequencies, or in different propagation environments due to non-co-addressing at the network side, the same user equipment may measure different uplink timing advances over different carriers.
Inventors of the invention have found that the existing TA+AoA method is only applicable to a serving cell as a single-cell positioning method, where the positioning effect depends on measurement effects of the cell. In practice, the accuracy of measuring a TA and an AoA may be affected by factors including environment, signal strength, interference, etc., and there may be different multi-path effects at different frequencies. With the single-cell positioning method, the positioning precision is low.